Introduction
Levothyroxine (Synthroid, Levoxyl) is the standard treatment for hypothyroidism, used by millions of Americans to replace or supplement thyroid hormone production.
How Levothyroxine Works
Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4), which the body converts to the active form T3, regulating metabolism throughout the body.
Administration Tips
Take levothyroxine 30–60 minutes before breakfast, or 3–4 hours after a meal. Consistency is critical — take it the same way every day for reliable TSH control.
Drug and Food Interactions
Calcium, iron supplements, antacids, cholestyramine, and soy products can reduce absorption. Separate these by at least 4 hours from your levothyroxine dose.
TSH Monitoring
Check TSH 6–8 weeks after starting or adjusting the dose, then annually once stable. Target TSH is typically 0.5–2.5 mIU/L for most patients.
Brand vs. Generic
Both brand-name and generic levothyroxine are bioequivalent, but switching formulations can affect TSH. Try to remain on the same manufacturer’s product.
Symptoms of Under-Treatment
Persistent fatigue, weight gain, cold intolerance, constipation, and brain fog may indicate the dose needs adjustment.
Pregnancy and Thyroid
Thyroid hormone requirements increase 25–50% in pregnancy. TSH should be checked every trimester and the dose adjusted promptly.
Conclusion
Consistent daily use and regular TSH monitoring make levothyroxine one of the most reliably effective long-term medications available.